During the process of perforating an oil or gas well, a perforating gun assembly has to be lowered into and positioned properly in the wellbore. Quite often, the gun assembly will have to spend some time prior to firing in a fluid-filled environment in the wellbore. If the gun system develops a leak which allows wellbore fluids to enter the gun system, several things could happen which are not desirable. The system could misfire altogether, only partially fire, fire low order and thereby damaging downhole equipment or becoming stuck, and so on. Therefore, it is important that a gun system have no leaks.
A typical perforating gun assembly consists of one or more perforating guns, as well as possibly comprising some spacer sections. If the zone to be perforated is longer than the amount which could be perforated with a single gun, then multiple perforating guns are connected together to create a perforating gun assembly of the desired length. Further, if there is more than one zone is to be perforated, and there is some distance between the zones to be perforated, spacer sections are inserted between the guns in the gun assembly. These spacer sections have detonation cord running from end to end, to transfer the ignition through the spacer section to the next component.
In order for the explosive transfer to occur from one section to the next in the gun assembly, an explosive transfer system is employed. This could be an overlap of detonating cord, the use of boosters either overlapped or end to end, or other known methods.
Typically there are seals (usually o-rings) at each point where the guns are connected together to prevent leaks and protect the inside of the gun system for wellbore fluids. It has been possible in the past to pressure test perforating guns and spacers prior to running into a wellbore. However, the length of test equipment was usually limited. In order to test the various portions of the gun assembly some type of temporary connection is made at the ends of the guns so that the guns may be externally pressure tested. At some time prior to running into the wellbore the temporary connection is disconnected so that the guns may be coupled together for running into the wellbore. Once these temporary connections are undone, the pressure test at that temporary connection point (now gun connection point) is void. When perforating guns are coupled together to run into the wellbore, this connection point between the guns would then be untested. If testing of this connection point is desired, the only option is to test at the well site, which is highly undesirable. The untested connections poise a much higher leak risk than the tested connections.
Therefore, it is an object of the invention to develop a system which would eliminate any untested connections within the gun assembly which could serve as leak paths that could damage the guns.
It is further an object of the invention to have a method and apparatus which would allow all required pressure testing of a gun assembly to be accomplished in a specifically designated safe area away from the well.
It is further an object of the invention to have a method and apparatus whereby all possible critical leak path connections in a gun assembly can be pressure tested, then not reopened prior to running into the wellbore.